National Bank of Canada (TSX:NA) is exploring options including a sale of Advanced Bank of Asia Limited, which could be valued at more than $2 billion in a deal, according to people familiar with the matter. The Montreal-based bank has held initial discussions with advisers on a strategic review for one of Cambodia?s biggest lenders, said the people, asking not to be identified as the process is private. Other options include minority or majority stake sales, the people said.